Today, I was babysitting my 6-year-old brother and was playing Mario. When I won, he called me a cunt. I was in shock and asked him where he learnt the word. He said from me when I was driving. He then told my mum that I taught him a new word. Easy to say, I'm in big trouble. FML

For those jumping down OP's throat saying "YDI for swearing in front of kids" blahblah.. So you're telling me that out of anger or spur of the moment, you have never once in your life slipped a cuss word while a child was nearby?
If the little brother was old enough to know it wasn't appropriate, then he is old enough to learn how to and when to use swear words. You don't protect children by keeping them ignorant. You protect them by educating them.

I think you've learned two things here:
1. Don't curse in front of children.
2. Don't beat your little brother at video games.
He sounds very competitive as well. A four letter word to describe someone who takes competition this far comes to mind, but you just never know who's going to read these, so I'll leave it up to reader interpretation.

Completely off topic, but is anyone else getting annoyed with the video ad at the top of the page? Have video ads, fine, but at least make them static like the others. The random expanding/collapsing is driving me nuts.

I'm going to say Your Life Sucks. Plenty of places he could have heard that word not just from you, such as quite a bit of the stuff called "music", played on the radio. But still try to watch what you say around him in future to be on the safe side.